1. Field of the Invention
The present invention relates to electrical control cables, or power cables, used to transmit currents.
2. Description of the Prior Art
Such cables are used in various fields of industry, such as the automotive industry, for example, where they are assembled into harnesses for electrical power supply and/or electrical control of various equipments. These cables must therefore in particular be as light as possible and have a small overall size whilst preserving good mechanical strength.
Such cables are conventionally formed by a plurality of copper strands, generally twisted to form a stranded conductor, so as to increase the flexibility of the cable, and surrounded by an insulative sheath, obtained by extrusion, for example. FIG. 1 shows one example of such a cable 1, seen in cross section, produced from seven identical copper strands 20 surrounded by a circular section insulative sheath 30. To give a rough idea, the diameter of the cable is typically of the order of 1.6 mm and the copper strands 20 each have a diameter of the order of 0.3 mm.
The advantages of a cable with the above structure lie essentially in the simplicity of the fabrication process, but also in the fact that it enables reliable crimping of connectors. In fact, it suffices to strip the cable locally by removing a portion of the insulative sheath 30 at the place where the connector is to be located, and then to compress mechanically a bush of the connector around the stripped cable section.
On the other hand, it has been realized that the above cable uses an excessive quantity of copper compared to the real requirements corresponding to the quantity of current to be transmitted by the cable. To be more precise, close to half the copper in the above cable structure is used to increase the tensile strength of the cable, and also to guarantee effective crimping.
Now, copper is costing more and more and it is important to find new cable structures that reduce as much as possible the quantity of copper used.
Various composite cable solutions are known already in which copper strands are combined with a non-conductive material core.
The major drawback of these various composite cable solutions lies in the fact that they all necessitate a fabrication process that is specific to them, with fabrication of dedicated tools for implementing the method. Thus the use of a smaller quantity of copper, which should decrease the cost of the cable, leads in the end to an increase in cost in terms of the fabrication process.
The object of the present invention is to propose a new power cable or electrical control cable structure of compact overall size, low weight and good mechanical strength, which can be fabricated with the same tools as a cable according to FIG. 1.